This invention relates to radiation sources for infrared (IR) spectrometry. In general, it is concerned with providing maximum radiation throughput in an interferometer spectrometer, using the minimum amount of power at the radiation source.
Infrared radiation sources for interferometer spectrometers have generally been either globars, which are rods heated by electric current, or coated electrical coils, such as those supplied by Buck Scientific.
The globar is described on page 2-27 of the Infrared Handbook as "a rod of bonded silicon carbide usually capped with metallic caps which serve as electrodes for the conduction of current through the globar", causing it to heat, "yielding radiation at a temperature above 1000.degree. C.". While a globar has a fairly good emissivity throughout the IR region, its power consumption is high (e.g., 200 watts), requiring that its mounting structure be water cooled both to limit heating of the instrument and to preserve the metallic electrodes. Thus, both the structure and its power consumption are costly.
Ceramic coated coilforms, such as those supplied by Buck Scientific, are small diameter, relatively long coils, usually placed inside an insulating housing. They have a lower power consumption (e.g., 42 watts) than globars; and they can be air-cooled, rather than water-cooled. However, the coilform radiation source has several drawbacks, including (a) possible effects on instrument operation due to radiated heat, (b) the requirement for a flow of outside air, and (c) the requirement for a special electrical power supply.
In general, the power sources used in interferometer spectrometers have not been well-designed for that use, and have caused significant waste of power and various accompanying disadvantages.